As a fuel, $\mathrm{H}_{2}(g)$ produces only nonpolluting $\mathrm{H}_{2} \mathrm{O}(g)$ when

it burns. Moreover, it combines with $\mathrm{O}_{2}(g)$ in a fuel cell (Chapter 21 ) to provide electrical energy.

(a) Calculate $\Delta H^{\circ}, \Delta S^{\circ},$ and $\Delta G^{\circ}$ per mole of $\mathrm{H}_{2}$ at 298 $\mathrm{K}$ .

(b) Is the spontaneity of this reaction dependent on $T ?$ Explain.

(c) At what temperature does the reaction become spontaneous?

## Discussion

## Video Transcript

No transcript available

## Recommended Questions

From the values given for $\Delta H^{\circ}$ and $\Delta S^{\circ},$ calculate $\Delta G^{\circ}$ for

each of the following reactions at 298 $\mathrm{K}$ . If the reaction is not spontaneous under standard conditions at 298 $\mathrm{K}$ , at what temperature (if any) would the reaction become

spontaneous?

$$

\begin{array}{l}{\text { (a) } 2 \mathrm{PbS}(s)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{PbO}(s)+2 \mathrm{SO}_{2}(g)} \\ {\Delta H^{\circ}=-844 \mathrm{kk} ; \Delta S^{\circ}=-165 \mathrm{J} / \mathrm{K}} \\ {\text { (b) } 2 \mathrm{POCl}_{3}(g) \longrightarrow 2 \mathrm{PCl}_{3}(g)+\mathrm{O}_{2}(g)} \\ {\Delta H^{\circ}=572 \mathrm{kJ} ; \Delta S^{\circ}=179 \mathrm{J} / \mathrm{K}}\end{array}

$$